/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hdfs.server.protocol;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
import org.apache.hadoop.security.KerberosInfo;

/** An inter-datanode protocol for updating generation stamp
 */
@KerberosInfo(
        serverPrincipal = DFSConfigKeys.DFS_DATANODE_KERBEROS_PRINCIPAL_KEY,
        clientPrincipal = DFSConfigKeys.DFS_DATANODE_KERBEROS_PRINCIPAL_KEY)
@InterfaceAudience.Private
public interface InterDatanodeProtocol {
    public static final Log LOG = LogFactory.getLog(InterDatanodeProtocol.class);

    /**
     * Until version 9, this class InterDatanodeProtocol served as both
     * the interface to the DN AND the RPC protocol used to communicate with the
     * DN.
     *
     * This class is used by both the DN to insulate from the protocol
     * serialization.
     *
     * If you are adding/changing DN's interface then you need to
     * change both this class and ALSO related protocol buffer
     * wire protocol definition in InterDatanodeProtocol.proto.
     *
     * For more details on protocol buffer wire protocol, please see
     * .../org/apache/hadoop/hdfs/protocolPB/overview.html
     */
    public static final long versionID = 6L;

    /**
     * Initialize a replica recovery.
     *
     * @return actual state of the replica on this data-node or
     * null if data-node does not have the replica.
     */
    ReplicaRecoveryInfo initReplicaRecovery(RecoveringBlock rBlock)
            throws IOException;

    /**
     * Update replica with the new generation stamp and length.
     */
    String updateReplicaUnderRecovery(ExtendedBlock oldBlock, long recoveryId,
                                      long newLength) throws IOException;
}
